1. Field of the Invention
The present invention relates to a presentation system for giving a presentation while indicating a point on a screen using a projector such as a liquid crystal projector. More particularly, the present invention relates to the development of a new pointer.
2. Description of the Related Art
When making a presentation for a lecture or the like using a liquid crystal projector, a laser pointer which indicates a point on a screen by projecting a laser beam is often used. A laser pointer of this type has, however, the following disadvantages. Shake greatly and adversely influences the pointing operation, thereby making the point unstable. A laser beam may be erroneously projected to be hazardously incident on the eyes of the audience. In addition, the shape of the point is limited to simple shapes such as a circle and a line, which cannot satisfy the demand for changing the shape of the point according to the user's preference.
To solve these disadvantages, various proposals have been conventionally made. For example, according to Japanese Patent Unexamined Application Publication No. 8-286147 (to be referred to as “Reference (1)” hereinafter), a rotating disk having a plurality of refracting grids for refracting a laser beam is rotated by a driving motor so that the laser beam is scanned by the refracting grids to enable the formation of a point into an arbitrary shape. In addition, the gyro effect of the rotation disk can reduce shaking. As safety measures, Japanese Patent Unexamined Application Publication No. 10-4228 (to be referred to as “Reference (2)” hereinafter) discloses that the projection of laser beam may be automatically turned on and off according to the brightness of a laser beam projection target (such as a screen) and that the laser beam is projected only if the brightness of the target exceeds a preset threshold value. Furthermore, Japanese Patent Unexamined Application Publication No. 2000-321530 (to be referred to as “Reference (3)” hereinafter) discloses a technique for detecting a vertical or horizontal angle and projecting laser beam only if the detected angle is within a predetermined range.
According to the laser pointer disclosed by Reference (1), the number of parts is relatively large, so that the weight of the laser pointer is increased and it is difficult to make the laser pointer small. Besides, since the laser pointer is forced to be operated while resisting moment which is generated by the rotation disk, it is not easily handled. Furthermore, although the shape of the point can be changed, it is difficult to increase variations in the shape of the point and to transform the laser beam into light of a complicated shape. According to the safety measures disclosed by References (2) and (3), if the laser point cannot be accurately operated, laser beam is projected. Due to this, these measures do not thoroughly ensure safety. That is, according to Reference (2), there is sometimes a location, other than the screen, having a brightness which exceeds the threshold value, depending on the lighting conditions of the place of a meeting or the like. If an audience member or the like is present at the location, laser beam may possibly be projected onto the audience member. According to Reference (3), an audience member is sometimes present within a laser beam projection angle, depending on the place of a meeting or the like such as a tiered seat or an upstairs seat. In this case, the laser beam may possibly be projected onto the audience member.